Hollow-porous nanospheres of ZnMn2O4 spinel: A high energy density cathode for rechargeable aqueous battery

Well-controlled hollow-porous nanostructures can provide enhanced charge storage capacity owing to the rapid diffusion of electrolyte ions into their interior. However, interface engineering of stable hollow-porous nano-structures with reversible faradaic reactions for efficient energy conversion/storage devices is still a challenge. Herein, we report solvothermal synthesis of spinel ZnMn2O4 with a hollow-porous spherical (ZMO(HS)) morphology. The formation mechanism of such a hierarchical nanostructure has been discussed. The ZMO(HS) exhibits a specific capacity of similar to 187 mAh g(-1) at a current density of 2 A g(-1) when tested as a faradaic electrode (vs Pt) for a rechargeable aqueous battery (RAB) in alkaline electrolyte. Furthermore, a full cell RAB constituting of ZMO(HS)//activated carbon (AC) demonstrates energy and power densities of similar to 215.7 Wh Kg(-1) and similar to 1184.5 W kg(-1) respectively, with ultra-long cycling stability (similar to 106% capacitance retention after 10,000 cycles), making it a very promising material for next-generation energy storage device applications.